As those who have been following along with our "minimum blimp" project to create the cheapest possible autonomous aerial robot (by adding an open source autopilot to a toy RC blimp), maintaining altitude in the face of air currents and temperature gradients has been a continuing challenge. The main problem with the toy RC blimps we start with is that they have a single tiny vertical motor and prop to control altitude, and unless you've trimmed the blimp exactly right and conditions don't change, that's not enough to reliably keep the blimp off the floor and away from the ceiling.
The best way to increase the vertical "authority" or control power is to get the two differential thrust props on each side to also do some vertical work, by tilting up or down along with their usual job of driving the blimp forward, back and right and left. Such tilting props are called "vectoring thrusters" and they're what the expensive blimps use. But on the cheap toy blimps that we start off with, the shaft that holds the two horizontal thrusters is glued and screwed into place.
No fear. Converting this shaft into one that can rotate is a simple matter of five pieces of Lego and a small RC servo. You can see it work in the video above, but here are some shots to show how to make it.
Before (typical toy blimp gondola, with RC equipment stripped out):
Parts needed (Lego Technic parts and one servo): Cut the blimp motor shaft in half and insert the Lego rod, with the gear and two Lego beams on it. Cut out a bit more room in the gondola and glue the two beams in. The shaft can now rotate: Now drill out the Lego gear to fit the servo shaft, screw it on, and then glue the servo on top of the Lego beams (depending on the size of your servo you might need a little plastic wedge to get the right spacing):That's it! Needless to say in the autonomous version the onboard autopilot will drive that servo, not a RC transmitter. But you get the idea. If the two vectoring thruster do the trick of altitude hold, I may remove the vertical thuster entirely to save weight (and two I/O pins). If I need even more vertical control, I'll keep all three going.
Comments
Not much hope here(such a old thread) but I'll give it a shot :) The blimp I am working on has no trust vectoring. Instead has reversed trust speed controllers for each motor up/down forward/backward and Yow. There is no roll axis. I wander if there is some APM/Pix4 template firmware for blimps developed or some way to customize it which does not involve computer programming/code writing?
I am working on integrating thrust vectoring into my brushless motor fighter planes, but this is proving very difficult... That plane I used a motorcycle mount just to handle the weight. Hopefully this project won't require any precision machining.
I'm thinking I may want to change the gear ratio to get a little more travel on the thrusters--I think I'm only getting about 100 degrees total. Can you estimate what the total angular range is of your RCGuys blimp thrusters?
You could move the 3rd thruster to one of the tail fins for stronger turn control - that's a fairly common configuration with larger blimps, though I haven't found a strong need for this.
The remain question is whether to keep the vertical thruster, and if so how to use both of them. Vectoring thrusters for small altitude changes and then kicking in the vertical thruster for extra power when I get too far away from the target?